Pipe Schedule Dimensions
Look up OD, wall thickness, and ID for standard pipe schedules. Covers ASME B36.10 (carbon & galvanized steel), ASME B36.19 (stainless steel), EN 10220 / DIN 2448 (metric European steel pipe), EN 10255 / DIN 2440(threaded steel), ASTM B88 and EN 1057(copper), ASTM D1785 (PVC), ASTM D3035 and EN 12201 / ISO 4427 (HDPE), and AWWA C151 (ductile iron).
Standard: ASME B36.10
| NPS | DN | OD (mm) | Wall (mm) | ID (mm) |
|---|---|---|---|---|
| 1/2" | 15 | 21.34 | 1.65 | 18.03 |
| 3/4" | 20 | 26.67 | 1.65 | 23.37 |
| 1" | 25 | 33.4 | 1.65 | 30.1 |
| 1-1/4" | 32 | 42.16 | 1.65 | 38.86 |
| 1-1/2" | 40 | 48.26 | 1.65 | 44.96 |
| 2" | 50 | 60.32 | 1.65 | 57.02 |
| 2-1/2" | 65 | 73.02 | 2.11 | 68.81 |
| 3" | 80 | 88.9 | 2.11 | 84.68 |
| 3-1/2" | 90 | 101.6 | 2.11 | 97.38 |
| 4" | 100 | 114.3 | 2.11 | 110.08 |
| 5" | 125 | 141.3 | 2.77 | 135.76 |
| 6" | 150 | 168.27 | 2.77 | 162.74 |
| 8" | 200 | 219.07 | 2.77 | 213.54 |
| 10" | 250 | 273.05 | 3.4 | 266.24 |
| 12" | 300 | 323.85 | 3.96 | 315.93 |
| 14" | 350 | 355.6 | 3.96 | 347.68 |
| 16" | 400 | 406.4 | 4.19 | 398.02 |
| 18" | 450 | 457.2 | 4.19 | 448.82 |
| 20" | 500 | 508 | 4.78 | 498.45 |
| 24" | 600 | 609.6 | 5.54 | 598.53 |
About Pipe Schedules
A pipe schedule defines the wall thickness of a pipe for a given nominal pipe size (NPS). Higher schedule numbers indicate thicker walls and higher pressure ratings. The most commonly used schedule is Schedule 40 (also called "Standard" weight for carbon steel).
NPS (Nominal Pipe Size) is a North American designation that loosely refers to the pipe diameter. For NPS 14 and above, NPS equals the actual outside diameter in inches. For smaller sizes, the relationship is nominal — the actual OD is standardized but does not match the NPS number.
DN (Diameter Nominal) is the metric equivalent of NPS, expressed in millimeters. DN 100 corresponds to NPS 4, DN 150 to NPS 6, etc.
Standards Covered
- ASME B36.10
- Welded and seamless wrought steel pipe (carbon & galvanized)
- ASME B36.19
- Stainless steel pipe (5S, 10S, 40S, 80S schedules)
- EN 10220 / DIN 2448
- Metric steel pipe (DN 6 - DN 600), standard and heavy wall
- EN 10255 / DIN 2440
- Threaded steel pipe for water/gas (DN 6 - DN 150), series L/M/H
- ASTM B88
- Seamless copper water tube (Type K, L, M)
- EN 1057
- Copper tube for water & gas, OD 6 - 267 mm
- ASTM D1785
- PVC plastic pipe, Schedules 40 and 80
- ASTM D3035
- HDPE pipe by SDR (Standard Dimension Ratio)
- EN 12201 / ISO 4427
- PE 100 HDPE for water supply, SDR 7.4 - 33 (PN 25 - PN 5)
- AWWA C151
- Ductile iron pipe (Class 150, 250, 350)
Column Definitions
- NPS
- Nominal Pipe Size (inches)
- DN
- Diameter Nominal (mm)
- OD
- Outside diameter
- Wall
- Wall thickness
- ID
- Inside diameter (OD minus 2x wall thickness)
Data source and basis
- Dimensions are transcribed from the current editions of the governing standards: ASME B36.10M (welded and seamless wrought steel pipe) and ASME B36.19M (stainless steel pipe) — transcribed from the 2018 editions; the 2022 editions leave the dimension tables for these sizes unchanged, ASTM B88 (seamless copper water tube), EN 10255:2004 (threaded steel tube, Series L/M/H), EN 10220 (steel tube outside diameters and walls), EN 12201 / ISO 4427 (PE pipe by SDR) and AWWA C151 (ductile iron).
- Outside diameter and wall thickness are the stored values; the inside diameter is derived as OD − 2 × wall from the nominal wall. ASME B36.10 permits a −12.5 % mill tolerance on wall — 0.89 mm on the 7.11 mm wall of a 6″ Sch 40 pipe — so a real bore can be up to about 1.8 mm larger in diameter than tabulated.
- ASME sizes are stored as the exact inch value × 25.4 mm and shown to three decimals (168.275 mm, not 168.3), so the metric column is a conversion of the standard's inch figures rather than the rounded metric series some catalogues print.
- Only the schedules and sizes in common use are carried; a blank cell means that combination is not made or was not transcribed, not that it does not exist in the standard.
- This is the same database the editor's pipe panel, the schedule pickers on the calculators and the solver read — a bore chosen here is the bore the simulation uses.
If you find a cell that disagrees with your copy of the standard, please report it with the edition and page — corrections are checked against the standard before the table is changed.
Frequently Asked Questions
What does pipe schedule mean?
Pipe schedule is a dimensionless number that relates to the wall thickness of a pipe for a given nominal pipe size (NPS). Higher schedule numbers mean thicker walls and higher pressure ratings. Common schedules include Sch 5, 10, 40, 80, and 160. Schedule 40 is the most common for general industrial use in carbon steel.
What is the difference between NPS and actual pipe OD?
NPS (Nominal Pipe Size) is a label, not a measurement. For NPS 1/8 through NPS 12, the outside diameter (OD) does not equal the NPS value — for example, NPS 2 pipe has an OD of 2.375 inches. For NPS 14 and larger, the OD equals the NPS value in inches. The OD stays constant across all schedules for a given NPS; only the wall thickness (and therefore ID) changes.
Which pipe schedule should I use for steam?
For low-pressure steam (up to 15 psig), Schedule 40 carbon steel is typical. Medium-pressure steam (15-150 psig) often uses Schedule 40 or 80. High-pressure steam (above 150 psig) may require Schedule 80, 120, or 160 depending on temperature and pressure. Always verify against ASME B31.1 (power piping) or B31.3 (process piping) minimum wall thickness calculations for your specific conditions.
What is the difference between carbon steel and stainless steel pipe schedules?
Carbon steel pipe follows ASME B36.10 and includes schedules from 5 through 160 plus standard (Std), extra strong (XS), and double extra strong (XXS). Stainless steel pipe follows ASME B36.19 and uses schedules 5S, 10S, 40S, and 80S. The 'S' schedules have the same OD as carbon steel but may have different wall thicknesses. For sizes NPS 12 and below, Sch 40S equals Sch 40.
How do I convert between metric (DN) and imperial (NPS) pipe sizes?
DN (Diametre Nominal) is the metric designation that corresponds to NPS. The conversion is not a direct unit conversion — DN 50 corresponds to NPS 2, not 50 mm. Common equivalents: DN 15 = NPS 1/2, DN 25 = NPS 1, DN 50 = NPS 2, DN 100 = NPS 4, DN 200 = NPS 8, DN 300 = NPS 12. This table shows both NPS and DN values for reference.
What is the difference between EN 10220 and ASME B36.10?
EN 10220 is the European/metric standard for steel pipe outside diameters; ASME B36.10 is the North American standard. Most common sizes overlap (DN 50 = NPS 2 = OD 60.3 mm), but some don't — for example DN 125 (OD 139.7 mm) has no exact NPS equivalent (NPS 5 is 141.3 mm), and DN 600 (610.0 mm) is slightly larger than NPS 24 (609.6 mm). EN pipe is also specified by wall thickness in millimeters from EN 10216-1 (seamless) or EN 10217-1 (welded), rather than by schedule number. The EN 10220 entries in this table use the legacy DIN 2448 standard wall thickness for each DN — what most European suppliers carry as default stock.
What is the difference between ASTM B88 and EN 1057 copper tube?
ASTM B88 (Type K, L, M) is the North American copper water tube standard, with imperial-based OD progression (e.g. NPS 1/2 has OD 0.625 in / 15.9 mm) and three wall thicknesses. EN 1057 is the European copper tube standard for water and gas, using metric OD designations directly — a '22 mm tube' is 22.0 mm OD exactly. EN 1057 covers OD 6 mm to 267 mm and is used throughout EU plumbing, HVAC, and industrial water systems. The two standards are not interchangeable: EN 22 mm ≠ ASTM 3/4 in (which is 19.05 mm OD).
What is the difference between EN 10220 and EN 10255?
EN 10220 (formerly DIN 2448) is the general-purpose European standard for steel pipe outside diameters, covering DN 6 to DN 2200 and intended for any steel pipe application — process, structural, mechanical. EN 10255 (formerly DIN 2440 / DIN 2441) is specifically for non-alloy steel tubes suitable for welding and threading, used in water, gas, low-pressure steam, and fire-protection systems. EN 10255 covers DN 6 to DN 150 and is published in three thickness series: L (light), M (medium / DIN 2440 successor), and H (heavy / DIN 2441 successor). Most ODs are identical to EN 10220 but DN 150 differs: EN 10255 uses 165.1 mm while EN 10220 uses 168.3 mm. If your project specifies threaded connections or matches DIN 2440 historical practice, use EN 10255.
What is the difference between EN 12201 and ASTM D3035 HDPE?
Both standards specify HDPE pipe by SDR (Standard Dimension Ratio = OD ÷ wall), but use different OD progressions. ASTM D3035 follows the IPS (Iron Pipe Size) system shared with steel pipe — DN 100 HDPE has OD 4.5 in / 114.3 mm, matching NPS 4 carbon steel. EN 12201 / ISO 4427 follows a metric progression (20, 25, 32, 40, 50, 63, 75, 90, 110, 125, 140, 160, 180, 200, 225, 250, 280, 315 mm…) that doesn't match ASME steel sizes. EN 12201 is the dominant standard for water-supply HDPE in Europe and increasingly worldwide. Pipe is rated by both SDR and PN (nominal pressure in bar) — for PE 100 material: SDR 11 = PN 16, SDR 17 = PN 10, SDR 26 = PN 6.
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